The property of suitable refractory materials, known as thixotropy whereby the materials become liquid when subjected to vibrations and are converted to a solid state when the vibration ends, is utilised for lining metallurgical vessels with vibration of the lining material.
This lining technique has been introduced into the steel industry for lining tapping spouts in blast furnaces. The thixotropic refractory material is introduced into the tapping spout, caused to flow with the aid of a vibration template, and homogenised and compacted.
This technique has also been used in the foundry industry for lining ladles which are not very high. It has also been proposed to line ladles in steel plants in this manner. In lining ladles in steel plants, however, the lining predominantly used are either linings with refractory bricks or monolithic linings obtained by ramming or slinging refractory compounds. The reason is that the refractory lining of ladles, in which metallurgical treatments of the melt are also frequently carried out today, has to meet high requirements in respect of their durability. The refractory lining of ladles is destroyed predominantly by infiltration and slagging.
The liquid slags and the melt infiltrate the refractory lining, where reactions take place between slags/melt and the refractory material of the lining, these reactions resulting in destruction of the refractory lining. In addition to the refractoriness and the mineral composition, the density of the refractory thixotropic compound used is important with regard to the slag resistance of the refractory lining. Specialists have hitherto apparently been of the opinion that, in the case of ladles in steel plants, an adequate density of the refractory lining cannot be achieved by vibration.
Furthermore, steel ladles which today usually have capacities of from 80 to 320 tons possess linings which are 3 m high or more. With these lining heights, specialists are troubled not only by the problem of an adequate density of the lining, but also by the possibility that the lining which has been subjected to vibration will not itself possess sufficient strength after removal of the template and will collapse.
The compound disclosed as a refractory compound for lining ladles in steel plants is a pourable compound whose principal components are zirconium silicate, a siliceous raw material, for example fireclay, and an alumina binder, the total alumina content of the pourable material being restricted to 5-1.0% by weight (German Auslegeschrift No. 3,235,244, and Nippon Kokan Technical Report, Overseas No. 37, 1983, pages 51 to 53). A disadvantage is the relatively high porosity of 16.5 to 21.5 vol. % and the consequent insufficient slag resistance owing to greater infiltration. Furthermore, as a result of adding fireclay, the lining tends to shrink and is consequently susceptible to fracture. As a result of using an alumina binder, the compound contains water of crystallisation. It also contains free SiO.sub.2. This is disadvantageous because SiO.sub.2 is reduced in the presence of manganese-containing melts, and siliconisation of the steel occurs.
U.S. Pat. No. 4,292,084 discloses a refractory material for lining metallurgical vessels by vibrating the material to compact it, which can consist of zirconium silicate, tabular alumina, calcined kaolin and phosphoric acid.
These known compounds, however, have bulk densities of only between 2.35 and 2.50 g/cm.sup.3. Therefore the slag resistance must be considered insufficient. Because of the high water content of between 6.4 and 7.1%, the lining might collapse after it has been produced by the vibration process and the former has been withdrawn.